The present invention relates to a method of, and apparatus for, routing to a mobile station in a packet switched network arrangement. The present invention is applicable to, but not limited to, cellular communications systems such as the Universal Mobile Telecommunication System (UMTS) currently under standardisation.
One type of communications system is a cellular communications system. In a cellular communications system, the area over which service is provided is divided into a number of smaller areas called cells. Typically, each cell is served from a base transceiver station (BTS) which has a corresponding antenna or antennas for transmission to and reception from a user station, normally a mobile station. An established harmonised system cellular radio communication system is GSM (Global System for Mobile Communications). A further harmonised system currently being defined is the universal mobile telecommunication system (UMTS), which is intended to provide a harmonised standard under which cellular radio communications networks and systems will provide enhanced levels of interfacing and compatibility with other types of communications systems and networks. In addition to speech and data services, increased provision of multimedia communications will be provided for. It is also expected that within the framework of developments such as UMTS or the like, cellular radio communication systems will increasingly interface with information networks such as the Internet.
Public data networks or information networks such as the Internet operate by the well known method of packet switching. Information to be transmitted across the Internet is packetized. The Internet consists of many nodes or Internet routers. A packet switching route is established between a source node and a destination node. Various methods of determining the routes are known. One method is called hop-by-hop routing. This is a dynamic method in which each Internet router makes its own decision about which next router to send the route forming details to where the route details can be in the form of a datagram. Another known method is source routing. Under source routing the route is selected by the source node for a certain data stream. In networks employing datagrams, some or all of the route from source to destination is explicitly stated in the datagrams. Both hop-by-hop and source routing are implemented in, for example, the Internet Protocol (IP). Two forms of source routing are used in IP networks. The first is strict source routing. Under strict source routing, a sender specifies the exact path that an IP datagram must follow. If an Internet router encounters as a next hop in the source route, a node that is not on the specified route, an ICMP (Internet Control Message Protocol) source route failed area message is returned. The second form is loose source routing. Under loose source routing the sender specifies a list of IP addresses that a datagram must traverse, but the datagram can also pass through other Internet routers between any two addresses in the list.
A cellular communications network can interface with a packet switched network arrangement such as the Internet via an Internet router serving as a gateway to the cellular communications network. Thus, when information is to be communicated to a mobile station in a cellular communications network or system, the route is established to the appropriate Internet router serving as the gateway of the cellular communications network.
The interaction between a mobile station in a cellular communications network and a general packet switched network arrangement, as described above, creates a broad range of new engineering problems and challenges. One challenge is to consider whether previously known methods of performing the routing within the packet switched network arrangements, such as the Internet, can be advantageously replaced or modified in the light of the different operating factors introduced by the mobility of a user of a mobile station in a cellular communications system.
In the light of the above, the present inventor has envisaged how routing in a packet switched network arrangement can be handled when the movement of a mobile station during receipt of information leads to the service being handed over from a first gateway to a second gateway. In particular the present inventor has envisaged that it would be advantageous to involve aspects of quality of service (QoS) within such cellular communications networks which may be affected by routing requirements introduced by the handover between gateways. Some examples of quality of service parameters that can be of significance in cellular communications are delay, jitter, bit loss ratio and bit error rate.
According to a first aspect of the present invention, there is provided a method of routing to a mobile station in a packet switched network arrangement. An initial packet switching route provided to a first cellular communications network in which a mobile station is receiving service is extended, in the event that handover of service to a second cellular communications network requires a change in the route, thereby forming an extended packet switching route, and thereafter, dependent on a level of quality of service determined for the extended route, a new packet switching route is formed to the mobile station. The various packet switching routes are established to packet switching nodes serving as gateways to the respective cellular communications networks. The different cellular communications networks are served via different gateways.
One or both of the cellular communications arrangements served by different gateways can be a UMTS network.
The various routes are formed from a source in a packet data network forming part of the packet switched network arrangement. The packet data network can comprise an information network such as the Internet.
The quality of service parameter can be additive over the various routes. This is particularly relevant when it is additive over the extended route. The quality of service parameter can comprise delay, jitter, bit loss ratio or bit error rate. Alternatively, a quality of service parameter can comprise a function of two or more of the above-mentioned parameters.
An achieved or measured level of quality of service can be compared to a threshold, and if the quality of service achieved on the extended route is below the threshold, the new replacement route is formed. The threshold can vary according to the type of data being transmitted or provided by the source.
The initial route can be formed by any appropriate routing method, including hop-by-hop routing, strict source routing and loose source routing.
The determination of the quality of service can be performed by the mobile station or by a network management entity. Similarly the decision to form a new route can be determined by the mobile station or a network management entity.
According to another aspect of the invention, there is provided an apparatus for carrying out routing to a mobile station in a packet switched network arrangement. The apparatus comprises means for forming an initial packet switching route to a first cellular communications gateway providing the service to a mobile station, means for extending, in response to the first cellular communications gateway handing over service to a second cellular communications gateway, the initial route thereby forming an extended packet switching route, and means for forming, dependent on the quality of service, a new packet switching route to the second cellular communications gateway to replace the extended route.
The extension to the initial route, and the entirely new replacement route, can each in themselves be formed by any appropriate route forming method, including hop-by-hop routing, strict source routing and loose source routing.
According to yet another aspect of the invention, there is provided a storage medium storing processor implementable instructions for controlling a processor to carry out any of the above described methods.
According to yet another aspect of the invention, there is provided a signal carrying processor implementable instructions for controlling a processor to carry out any of the above methods.
According to yet another aspect of the present invention, there is provided a cellular communications mobile station with means for analysing or determining a quality of service it is receiving when it is receiving that service through an extended communications route due to movement, and means for requesting a new communication route if that quality of service is insufficient.
The present invention advantageously retains a routing connection in a simple fashion when handover is required, yet then allows satisfactory quality of service to be maintained thereafter. Furthermore, the present invention avoids wasteful use of resources employed in establishing a new route, if the extended route is sufficient in terms of quality of service. The present invention is particularly advantageous in coping with additive quality of service parameters.
Additional specific advantages are apparent from the following description and figures.